1. Field of the Invention
The present invention relates to cycle pedal crank extensions, and more particularly, to an apparatus which synchronically extends the pedal crank twice at one cycle and provides an adjustable mechanism for variable Gemini trace on different usage.
2. Description of the Related Art
Cycling exercise has very long history on human activity. Some variable speed gears and sprocket systems are popular with the cyclists to adjust the work out for different road condition. They change the ratio between the front and the rear gear or sprocket through chain or belt to get higher efficiency, or change a different number of revolutions made respectively by the crank to communicate a difference of velocity. Furthermore, some extending pedal mechanisms are provided to lowdown the exertion at the front downward stroke. The cyclists get the minimum of exertion if the pedal arm could extend longer. If the power source works best over a relatively restricted range of output transmission, the crank system can be extremely beneficial.
Generally, the distance of pedal crank has some limitations to fit the requirements of practical usage. Pedal crank of long rotating distance can produce bigger torque and save power, but long crank arm leads to increase the size of entire crank device as well as its working space. The crank will be perfect if the rotating distance of the pedal crank could increase at horizontal position and decrease at vertical position for leg movement so as to provide more exertion at pedaling path.
Stationary cycling exercise is wildly used for cardiovascular exercise. While the range of motion provided by a cycling exercise is fairly limited, these exercising motions are not always optimal and can induce excessive joint or muscle stress. In these years, many elliptical cycles or trainers are wildly introduced. Some inventions emphasized the elliptical emotion are more similar to human walking. Most of these exercise devices utilize two or three exercising motions, like circular (single crank path), arcuate (lever path), or linear (slider or roll path). These three motions rarely duplicate functional and real world motions in an accurate manner to dissatisfy the user. In addition, the machines are complicated and huge for operation because of the complicated mechanism. An improved mechanical system, which can be used in various types of exercising machines and generate a controlled closed exercise motion more closely to simulating functional and real world activities, is required. It is also desirable that exercise device is relatively easy to use and to be low-cost in production.
Pedaling systems for transferring leg drive power of a cyclist to exercise devices are popular. The normal sprocket gear of circular device is coupled by a chain to a driver sprocket gear to rotate the rear wheel or a flywheel. Pedal cranks are located on each side of the drive sprocket gear, oriented 180 apart from one another. Each pedal in turn affords half input at one cycle to drive the wheel to rotate. The cyclist of the device rotates the drive sprocket by means of a circular cycling motion. Furthermore, the pedal crank mechanisms are improved to get more torque at front stroke for improving the efficiency. Many similar mechanisms use guiding cam, disc, or pulley to control variation of the pedal crank, and for example, U.S. Pat. No. 6,152,471 in the name of Kang et al. disclosed that some eccentric pans proceed variable pedal path. Meanwhile, there are some planetary gears or sprockets to accomplish the extension or orientation of the pedal crank. The mechanism is provided to improve efficiency of cycling and is therefore emphasized on the front stroke.
U.S. Pat. No. 5,433,680 disclosed an elliptical path pedaling system which has two circular driven members reciprocating in horizontal route, and it must be coupled with one or more chain linkages to perform the synchronic coordination of the cycle transmission.
In other case, many elliptical cycles and trainers are promoted for sale in market. These exercise machines, which utilize combined exercising motions, circular, arcuate, or linear, have been developed to simulate the motions of human skiing, walking, or running. The driving motion is the same. The pedal cranks rotate about a fixed axis or a center line around which either a sprocket wheel or the drive lever offsets are rotated to produce the driving power for moving the device to rotate. In addition, the elliptical pedal path is between an end of circular movement and the other end of reciprocating movement. U.S. Pat. No. 6,027,431 disclosed a linkage assembly, which has rotation of an adjustable crank length at an end and suspended reciprocation at the other end of the device to generate adjustable elliptical movement. It is similar that most of the elliptical devices take more space than normal cycle exercise devices, and some linkages are hard to cover because of complicated mechanism, especially for the elongated pedal. It is major concern for the exercise devices on safety and convenience to provide suitable mechanism.
An improved mechanical system, which can be used in various types of exercising devices, generates a controlled closed exercise motion more closely to simulate functional and real world activities, which provide the physical benefits of cycling without impact. It is, therefore, an object of this invention to provide an improved pedaling crank system which produces Gemini pedal trace similarly as an ellipse path from a cycling motion coupled with reciprocating inner crank motion.
It is a further object to provide an effective pedaling crank system for delivering a greater power for a long period of time during pedal operation cycle, which overcomes the disadvantages of the prior art noted above to be effective in operation, easy to use, and capable adaptation into a variety of different devices.
It is an additional object of this invention to provide an adjustable pedal trace mechanism more flexible for practical use on the exercise devices or the like.